For example, when an aged person stands up from a chair where he/she was seated, an apparatus for supporting his/her stand-up motion is proposed. In this apparatus, the stand-up motion is stably supported while the aged person's physical burden is reduced. However, if a person is not using his/her muscle strength for a long time, it is well known that the muscle strength of this part is quickly fallen. Namely, for a person having some remaining physical ability to stand up, over-support by this apparatus will make the person's muscle strength be fallen.